Like eating, investing is a very personal and variable undertaking. For example, some people skip breakfast, while others consider it the day's most important meal. When it comes to investing, some people happily invest in index funds and ETFs, while others trade cryptos, invest in options, or trade on margin. And some of our investing habits, like our eating habits, can be very unhealthy and lead to a lower quality of life. Nobody wants to be 200 pounds overweight or 50 pounds underweig...